6. Current treatment with either metformin alone or in combination with SU. The dose of the current treatment must be stable for at least 8 weeks prior to randomization. Patients being treated with metformin must be at their optimal or near-optimal dose (≥1500 mg/day ± 500 mg/day for a range of 1000 to 2000 mg/day), and patients being treated with SU must be receiving at least one half of the maximum approved SU dose;